1. Field of the Invention
The present invention relates to the field of valves, and systems using a plurality of solenoid actuators.
2. Prior Art
Embodiments of the present invention provide improved devices for fluid control in various applications. Typical examples include the control of a high pressure fuel injector, and hydraulic engine valve actuation systems. Two-way poppet valves (open and closed) are often used due to their low leakage characteristics. In many applications, it is highly desirable to use a three-way valve for improved performance and control, but this is difficult due to a three-way valve's inability to pressure balance completely unless it is a spool valve, which leaks excessively. For purposes of this disclosure, a three-way valve will be described as a valve coupling a source (S) passage to a control (C) passage or coupling the control passage to a vent (V), though other port identifications may be more appropriate depending on the use of the three-way valve.
The choices for a three-way valve are:
Spool valve. A spool valve can create the required hydraulic paths, but while in either position (S-C or C-V) the valve has a very short leak (seal) path from a high-pressure area to a vented area, which can lead to high system parasitic losses. This valve can be designed to have a hydraulic short circuit (momentarily coupling of source and vent when transitioning from one position to the other) or not, depending on the application. The advantages are primarily in its pressure balance, thereby requiring very low actuation forces, and in the ability to be designed to avoid the short circuit.
Three-way hard-seat valve (Poppet). This type of valve can have no leakage in either position, but when the valve is transitioning from one position to the other, there necessarily exists a direct flow path between the source and the vent that could lead to large losses of energy and system noise. This type of valve cannot be completely pressure balanced, and therefore requires greater actuating forces than a typical pressure balanced spool valve.
Two two-way hard-seat valves (Poppet). This option has no leakage and can have a direct flow path between the source and the vent or not, depending on control of the system. The disadvantage of this system is that twice as many control valves are needed to achieve three-way control, adding system and control complexity, and further requiring more room to package.
Thus the current choices and their disadvantages are:
Spool Valve: High static leakage.
Three-way hard-seat valve: High actuating force requirements (due to pressure imbalance) and short circuit loss.
Two, two-way hard seat valves: Cost and complexity.
Solenoid actuators for valves of various types are also well known. Such actuators may be single coil spring return, with or without magnetic latching or double coil, with or without magnetic latching (see U.S. Pat. Nos. 3,743,898 and 5,640,987). However configured, solenoid actuators generally have a relatively simple mechanical configuration, with the solenoid coils being relatively inexpensive to wind. However, in certain applications, the number of solenoid actuated valves preferably used may be relatively large, giving rise to quite a substantial wiring problem. Superimposed on this in certain applications is a combination of heat and vibration that can cause premature wiring failure, and thus possibly giving rise to unsatisfactory reliability of the system. One such application to which preferred embodiments of the present invention are directed is in diesel engines, and more specifically, to hydraulic engine valve actuation systems as are currently in development, and diesel engine fuel injection systems, as well as fuel air cells incorporating both hydraulic engine valve actuation and fuel injection in a single assembly for each engine cylinder. Because most diesel engines are multiple cylinder engines, such as 6 and 8 cylinder engines, each having intake valves, exhaust valves and a fuel injector, all three of which must be independently controlled for each cylinder, and preferably for greater flexibility each engine valve actuator and each fuel injector will have more than one solenoid valve, the number of solenoid valves preferably used in a multi-cylinder engine can be quite substantial. Accordingly, wiring of the individual solenoid coils to a harness for connection to a control box would be complicated and expensive and may not have the reliability inherent in the rest of the diesel engine.